Methanol rectification device based on multi-effect thermal coupling

Abstract

The utility model provides a methanol rectification device based on multi-effect thermal coupling. The methanol rectification device comprises a pre-rectification tower, a negative pressure rectification tower, a pressurization rectification tower, a secondary pressure rectification tower and a normal pressure rectification tower which are connected in sequence, the pre-rectifying tower, the pressurized rectifying tower, the secondary-pressure rectifying tower and the normal-pressure rectifying tower are respectively provided with a pre-tower reboiler, a pressurized tower reboiler, a secondary-pressure tower reboiler and a normal-pressure tower reboiler, the lower part of the negative-pressure rectifying tower is provided with a first negative-pressure tower reboiler and a second negative-pressure tower reboiler, and a gas phase extracted from the top of the secondary-pressure rectifying tower provides heat for the pre-tower reboiler; a gas phase extracted from the top of the pressurized rectifying tower provides heat for a secondary pressure tower reboiler and an atmospheric tower reboiler respectively; a gas phase extracted from the top of the pre-rectifying tower provides heat for a negative pressure tower reboiler I; a gas phase extracted from the top of the normal-pressure rectifying tower provides heat for a negative-pressure tower reboiler II; the energy utilization efficiency in the methanol rectification process can be remarkably improved, the production cost is reduced, the environmental pollution is reduced, and remarkable economic and social benefits are achieved.

Description

Technical Field

[0001] This application relates to the field of chemical engineering technology, and particularly relates to a methanol distillation device based on multi-effect heat coupling. Background Art

[0002] Methanol is a widely used basic chemical raw material in the chemical industry, and is applied in many fields such as fine chemicals, polymers, pesticides, pharmaceuticals, and energy, and has an extremely important position in the international chemical market; crude methanol usually contains light component impurities such as dimethyl ether and heavy component impurities such as ethanol and water. After various impurities are removed through the distillation process, refined methanol products that meet the quality requirements can be obtained; the energy consumption in the methanol distillation process accounts for about 20 - 30% of the total production energy consumption, which has a great impact on the product cost.

[0003] With the continuous growth of global energy consumption and the increasingly serious environmental problems, energy conservation and consumption reduction have become urgent problems to be solved in industrial production. In fields such as the chemical industry, refining industry, biochemical industry, environmental protection industry, and energy industry, methanol is an important chemical raw material and fuel, and the energy consumption in the distillation process during its production is relatively high. Therefore, it is of great significance to improve the energy utilization efficiency of the methanol distillation process.

[0004] Traditional methanol distillation processes usually adopt single-effect or multi-effect distillation technologies, but these technologies have certain limitations in heat energy utilization; single-effect distillation equipment is simple, but the energy consumption is high and the heat energy utilization efficiency is low; for double-effect distillation, more than 90% of enterprises currently use double-effect distillation, and its energy consumption is relatively high compared to multi-effect distillation and it is gradually being phased out. Although the multi-effect distillation on the market currently improves the heat energy utilization efficiency to a certain extent, there is still room for improvement in the energy-saving effect.

[0005] For example, a crude methanol five-column four-effect refining device with the application number 202320551853.9 discloses a solution, which includes a pre-distillation column, a vacuum column, a pressurized column, an atmospheric column, and a recovery column connected in sequence. A pre-distillation column reboiler, a vacuum column reboiler, a pressurized column reboiler, an atmospheric column reboiler, and a recovery column reboiler are respectively provided on the pre-distillation column, the vacuum column, the pressurized column, the atmospheric column, and the recovery column. Among them, the refined methanol extracted from the top of the pressurized column exchanges heat with the pre-distillation column reboiler and the atmospheric column reboiler, and the refined methanol extracted from the top of the atmospheric column exchanges heat with the vacuum column reboiler; the overall structure of this application is simple and the manufacturing cost of the equipment is low; the refined methanol extracted from the top of the pressurized column can not only exchange heat with the pre-distillation column reboiler, but also exchange heat with the atmospheric column reboiler; the refined methanol extracted from the top of the atmospheric column exchanges heat with the vacuum column reboiler. One effect is achieved through the pressurized column itself, the second and third effects are achieved through the heat coupling at the top of its tower, and the fourth effect is achieved through the coupling of the atmospheric column top and the vacuum column; and compared with the traditional methanol process, this application can reduce the steam specific consumption to 0.55 - 0.65.

[0006] In the above-mentioned patent application, only the heat of the refined methanol taken from the top of the pressurized column and the heat of the refined methanol taken from the top of the atmospheric column are utilized. Although the steam specific consumption is relatively low compared to the traditional methanol process, there is still room for improvement in the energy-saving effect.

[0007] In summary, a new technical solution is needed to solve the above technical problems. Summary of the Invention

[0008] This application provides a methanol rectification device based on multi-effect heat coupling, which includes a pre-rectification column, a vacuum rectification column, a pressurized rectification column, a sub-pressure rectification column, and an atmospheric rectification column connected in sequence. A pre-column reboiler, a pressurized column reboiler, a sub-pressure column reboiler, and an atmospheric column reboiler are respectively arranged on the pre-rectification column, the pressurized rectification column, the sub-pressure rectification column, and the atmospheric rectification column. A vacuum column reboiler I and a vacuum column reboiler II are arranged at the lower part of the vacuum rectification column. Among them, the gas phase taken from the top of the sub-pressure rectification column provides heat for the pre-column reboiler; the gas phase taken from the top of the pressurized rectification column provides heat for the sub-pressure column reboiler and the atmospheric column reboiler respectively; the gas phase taken from the top of the pre-rectification column provides heat for the vacuum column reboiler I; the gas phase taken from the top of the atmospheric rectification column provides heat for the vacuum column reboiler II.

[0009] As a preferred solution, the output end of the vacuum column reboiler I is connected with a pre-column reflux device.

[0010] As a preferred solution, the pre-column reflux device includes an extraction reflux tank. An extraction water pipeline is arranged on one side of the extraction reflux tank. A purge gas pipeline is arranged at the top of the extraction reflux tank. The bottom of the extraction reflux tank is connected with the upper part of the pre-rectification column through a pre-column reflux pipeline.

[0011] As a preferred solution, a vacuum column reflux device is arranged at the top of the vacuum rectification column.

[0012] As a preferred solution, the output ends of the sub-pressure column reboiler and the atmospheric column reboiler are respectively connected with a pressurized column reflux tank. The bottom of the pressurized column reflux tank is connected with the upper part of the pressurized rectification column through a pressurized column reflux pipeline. The pressurized column reflux pipeline is connected with the pressurized column refined methanol extraction pipeline.

[0013] As a preferred solution, the output end of the pre-column reboiler is connected with a sub-pressure column reflux device.

[0014] As a preferred solution, the sub-pressure column reflux device includes a sub-pressure column reflux tank. The bottom of the sub-pressure column reflux tank is connected with the upper part of the sub-pressure rectification column through a sub-pressure column reflux pipeline. The sub-pressure column reflux pipeline is connected with the sub-pressure column refined methanol extraction pipeline.

[0015] As a preferred solution, the output end of the vacuum column reboiler II is connected with an atmospheric column reflux device.

[0016] As a preferred solution, the atmospheric column reflux device includes an atmospheric column reflux drum. The bottom of the atmospheric column reflux drum is connected to the upper part of the atmospheric distillation column through an atmospheric column reflux pipeline, and the atmospheric column reflux pipeline is connected to the refined methanol extraction pipeline of the atmospheric column.

[0017] As a preferred solution, the pre-distillation column is respectively connected to a vacuum distillation column and a second vacuum distillation column. The vacuum distillation column and the second vacuum distillation column are connected to a pressurized distillation column. A second vacuum column reboiler is provided on the second vacuum distillation column, and the gas phase extracted from the top of the vacuum distillation column provides heat for the second vacuum column reboiler.

[0018] As a preferred solution, the output end of the second vacuum column reboiler is connected to a vacuum column reflux device.

[0019] As a preferred solution, the vacuum column reflux device includes a vacuum column reflux drum. The bottom of the vacuum column reflux drum is connected to the upper part of the vacuum distillation column through a vacuum column reflux pipeline, and the vacuum column reflux pipeline is connected to the refined methanol extraction pipeline of the vacuum column; the upper part of the vacuum column reflux drum is connected to a second-stage condenser at the top of the vacuum column through a top pipeline. The output ends of the second-stage condenser at the top of the vacuum column are respectively connected with a non-condensable gas extraction pipeline and a condensate pipeline. The condensate pipeline is connected to the vacuum column reflux drum, and a vacuum pump is provided on the non-condensable gas extraction pipeline.

[0020] As a preferred solution, a second vacuum column reflux device is provided at the top of the second vacuum distillation column. The second vacuum column reflux device includes a second vacuum column reflux drum. The bottom of the second vacuum column reflux drum is connected to the upper part of the second vacuum distillation column through a second vacuum column reflux pipeline, and the second vacuum column reflux pipeline is connected to the refined methanol extraction pipeline of the second vacuum column; the upper part of the second vacuum column reflux drum is connected to a second-stage condenser of the second vacuum column through a second top pipeline. The output ends of the second-stage condenser of the second vacuum column are respectively connected with a second non-condensable gas extraction pipeline and a second condensate pipeline. The second condensate pipeline is connected to the second vacuum column reflux drum, and a second vacuum pump is provided on the second non-condensable gas extraction pipeline.

[0021] As a preferred solution, a feed pipeline is provided on one side of the pre-distillation column, and a pre-column feed preheater is provided on the feed pipeline.

[0022] As a preferred solution, the bottom of the vacuum distillation column is connected to the pressurized distillation column through a vacuum column bottom extraction pipeline. A first-stage feed preheater for the pressurized column and a second-stage feed preheater for the pressurized column are successively provided on the vacuum column bottom extraction pipeline.

[0023] As a preferred solution, the input end of the pressurized column reboiler is connected to a steam pipeline, and the output end of the pressurized column reboiler is connected to a condensate pipeline.

[0024] As a preferred solution, the condenser pipeline sequentially passes through the secondary feed preheater of the pressurized column and the feed preheater.

[0025] In this application, the top heat of the pre-distillation column, pressurized distillation column, sub-pressure distillation column, and atmospheric distillation column is fully utilized, and the steam specific consumption is significantly reduced, with the consumption reduced to 0.5 - 0.55 tons of steam per ton of refined methanol, greatly reducing energy consumption. Moreover, through the effective recovery and utilization of heat, the thermal efficiency of the entire distillation system is improved, ensuring a reduction in the system operation cost, enhancing the economic benefits of the enterprise, and reducing the emissions of carbon dioxide and other pollutants, which conforms to the green environmental protection production concept. Preferably, the heat of the top of the vacuum distillation column is also utilized to further reduce the steam specific consumption to 0.4 - 0.45 tons of steam per ton of refined methanol, with a more significant energy-saving effect; the overall thermal efficiency of the system is further improved, the operation cost of the system is further reduced, and the environmental impact is further reduced, which is conducive to achieving sustainable development and environmental protection.

[0026] This application can significantly improve the energy utilization efficiency in the methanol distillation process, reduce production costs, and reduce environmental pollution, with significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of Embodiment 1 of this application;

[0028] Figure 2 is a schematic structural diagram of Embodiment 2 of this application;

[0029] 1. Pre - rectifying column; 2. Vacuum rectifying column; 3. Pressurized rectifying column; 4. Sub - pressured rectifying column; 5. Atmospheric rectifying column; 6. Feed pipeline; 7. Feed pre - heater of pre - column; 8. Bottom product pipeline of pre - column; 9. Feed pump of vacuum column; 10. Bottom product pipeline of vacuum column; 11. Feed pump of pressurized column; 12. Primary feed pre - heater of pressurized column; 13. Secondary feed pre - heater of pressurized column; 14. Bottom product pipeline of pressurized column; 15. Product pipeline of sub - pressured column; 16. Feed pump of atmospheric column; 17. Fusel oil product pipeline; 18. Waste water product pipeline; 19. Reboiler of pre - column; 20. Reboiler of pressurized column; 21. Reboiler of sub - pressured column; 22. Reboiler of atmospheric column; 23. First reboiler of vacuum column; 24. Second reboiler of vacuum column; 25. Top product pipeline of sub - pressured column; 26. Top product pipeline of pressurized column; 27. First top product pipeline of pressurized column; 28. Top product pipeline of pre - column; 29. Top product pipeline of atmospheric column; 30. Steam pipeline; 31. Condensate pipeline; 32. Extraction reflux tank; 33. Output pipeline of first reboiler of vacuum column; 34. Condenser at the top of pre - column; 35. Extraction water pipeline; 36. Relief gas pipeline; 37. Reflux pipeline of pre - column; 38. Reflux pump of pre - column; 39. Reflux tank of vacuum column; 40. Top product pipeline of vacuum column; 41. First condenser at the top of vacuum column; 42. Reflux pipeline of vacuum column; 43. Reflux product pump of vacuum column; 44. Refined methanol product pipeline of vacuum column; 45. Cooler at the top of vacuum column; 46. Refined methanol tank; 47. Top pipeline; 48. Second condenser at the top of vacuum column; 49. Non - condensable gas product pipeline; 50. Condensate pipeline; 51. Vacuum pump; 52. Output pipeline of reboiler of sub - pressured column; 53. Reflux tank of pressurized column; 54. Output pipeline of reboiler of atmospheric column; 55. Reflux pipeline of pressurized column; 56. Reflux product pump of pressurized column; 57. Refined methanol product pipeline of pressurized column; 58. Cooler at the top of pressurized column; 59. Output pipeline of reboiler of pre - column; 60. Reflux tank of sub - pressured column; 61. Reflux pipeline of sub - pressured column; 62. Reflux product pump of sub - pressured column; 63. Refined methanol product pipeline of sub - pressured column; 64. Output pipeline of second reboiler of vacuum column; 65. Reflux tank of atmospheric column; 66. Reflux pipeline of atmospheric column; 67. Reflux product pump of atmospheric column; 68. Refined methanol product pipeline of atmospheric column; 69. Cooler at the top of atmospheric column; 70. Second vacuum rectifying column; 71. First bottom product pipeline of pre - column; 72. Bottom product pipeline of second vacuum column; 73. Reboiler of second vacuum column; 74. Output pipeline of reboiler of second vacuum column; 75. Reflux tank of second vacuum column; 76. Top product pipeline of second vacuum column; 77. First condenser at the top of second vacuum column; 78. Reflux pipeline of second vacuum column; 79. Reflux product pump of second vacuum column; 80. Refined methanol product pipeline of second vacuum column; 81. Second top pipeline; 82. Second condenser at the top of second vacuum column; 83. Non - condensable gas product pipeline two; 84. Condensate pipeline two; 85. Waste water product pipeline two; 86. Bottom pump of second vacuum column; 87. Second vacuum pump. Detailed implementation manners

[0030] The following is combined with Figure 1 —2 The specific implementation methods of the utility model are described in detail. It should be noted that the specific implementation methods described here are only used to illustrate and explain the utility model, and are not used to limit the utility model.

[0031] Embodiment 1:

[0032] like Figure 1 As shown, the present application provides a methanol distillation device based on multi-effect thermal coupling, comprising a pre-distillation tower 1, a negative pressure distillation tower 2, a pressurized distillation tower 3, a secondary pressure distillation tower 4, and an atmospheric distillation tower 5 connected in sequence. More specifically, a feed pipeline 6 is provided on one side of the pre-distillation tower 1, and a pre-tower feed preheater 7 is provided on the feed pipeline 6. The crude methanol enters the pre-distillation tower 1 after being preheated by the pre-tower feed preheater 7; the bottom of the pre-distillation tower 1 is connected to the negative pressure distillation tower 2 through a pre-tower reactor extraction pipeline 8, and a negative pressure tower feed pump 9 is provided on the pre-tower reactor extraction pipeline 8; the bottom of the negative pressure distillation tower 2 is connected to the pressurized distillation tower 3 through a negative pressure tower reactor extraction pipeline 10, and the negative pressure tower reactor extraction pipeline 10 is sequentially provided with a pressurized tower feed pump 9. The material at the bottom of the negative pressure distillation tower 2 is preheated in sequence by the negative pressure distillation tower first-level feed preheater 12 and the negative pressure distillation tower second-level feed preheater 13, and then enters the negative pressure distillation tower 3; the bottom of the negative pressure distillation tower 3 is connected with the secondary pressure distillation tower 4 through the negative pressure distillation tower kettle extraction pipeline 14, and the negative pressure distillation tower kettle extraction pipeline 14 passes through the negative pressure distillation tower first-level feed preheater 12; the secondary pressure distillation tower 4 is connected with the atmospheric distillation tower 5 through the secondary pressure tower extraction pipeline 15, and the atmospheric pressure tower feed pump 16 is arranged on the secondary pressure tower extraction pipeline 15; a fusel alcohol extraction pipeline 17 is arranged on one side of the atmospheric distillation tower 5, and a wastewater extraction pipeline 18 is arranged at the bottom of the atmospheric distillation tower 5 for extracting wastewater that meets the standards.

[0033] A pre-fractionating column 1, a pressurized fractionating column 3, a secondary-pressure fractionating column 4, and an atmospheric-pressure fractionating column 5 are respectively provided with a pre-column reboiler 19, a pressurized-column reboiler 20, a secondary-pressure-column reboiler 21, and an atmospheric-pressure-column reboiler 22. A first vacuum-column reboiler 23 and a second vacuum-column reboiler 24 are arranged at the lower part of the vacuum fractionating column 2. Among them, the top of the secondary-pressure fractionating column 4 is connected to the input end of the pre-column reboiler 19 through a secondary-pressure-column top product pipeline 25. The gaseous refined methanol extracted from the top of the secondary-pressure fractionating column 4 serves as a heat source to provide heat for the pre-column reboiler 19. The top of the pressurized fractionating column 3 is connected to the atmospheric-pressure-column reboiler 22 and the secondary-pressure-column reboiler 21 respectively through a pressurized-column top product pipeline 26 and a first pressurized-column top product pipeline 27. The gaseous refined methanol extracted from the top of the pressurized fractionating column 3 serves as a heat source to provide heat for the atmospheric-pressure-column reboiler 22 and the secondary-pressure-column reboiler 21 respectively. The top of the pre-fractionating column 1 is connected to the input end of the first vacuum-column reboiler 23 through a pre-column top product pipeline 28. The gaseous refined methanol extracted from the top of the pre-fractionating column 1 serves as a heat source to provide heat for the first vacuum-column reboiler 23. The top of the atmospheric-pressure fractionating column 5 is connected to the second vacuum-column reboiler 24 through an atmospheric-pressure-column top product pipeline 29. The gaseous refined methanol extracted from the top of the atmospheric-pressure fractionating column 5 serves as a heat source to provide heat for the second vacuum-column reboiler 24. The pressurized-column reboiler 20 is heated by steam at 0.5 MpaG. Specifically, the input end of the pressurized-column reboiler 20 is connected to a steam pipeline 30, and the output end of the pressurized-column reboiler 20 is connected to a condensate pipeline 31. Preferably, the condensate pipeline 31 sequentially passes through a pressurized-column secondary-feed preheater 13 and a pre-column feed preheater 7. The pressurized-column reboiler 20 is heated by steam at 0.5 MpaG, and at the same time, the gaseous refined methanol at the top of the pressurized fractionating column 3 serves as a heat source to provide heat for the secondary-pressure-column reboiler 21 and the atmospheric-pressure-column reboiler 22, further optimizing the utilization of thermal energy.

[0034] The output end of the first vacuum-column reboiler 23 is connected to a pre-column reflux device. The pre-column reflux device includes an extraction reflux tank 32. The extraction reflux tank 32 is connected to the output end of the first vacuum-column reboiler 23 through a first vacuum-column reboiler output pipeline 33. A pre-column top condenser 34 is arranged on the first vacuum-column reboiler output pipeline 33. An extraction water pipeline 35 is arranged on one side of the extraction reflux tank 32. A purge gas pipeline 36 is arranged at the top of the extraction reflux tank 32. The bottom of the extraction reflux tank 32 is connected to the upper part of the pre-fractionating column 1 through a pre-column reflux pipeline 37. A pre-column reflux pump 38 is arranged on the pre-column reflux pipeline 37. The gaseous refined methanol extracted from the top of the pre-fractionating column 1 serves as a heat source to provide heat for the first vacuum-column reboiler 23. The material cooled after heat exchange with the first vacuum-column reboiler 23 is further cooled by the pre-column top condenser 34 and then enters the extraction reflux tank 32. Extraction water is introduced into the extraction reflux tank 32. The gaseous phase in the extraction reflux tank 32 is extracted through the purge gas pipeline 36. The liquid phase in the extraction reflux tank 32 is refluxed to the pre-fractionating column 1 through the pre-column reflux pipeline 37, improving the rectification accuracy of refined methanol.

[0035] A negative-pressure tower reflux device is provided at the top of the negative-pressure rectification tower 2. The negative-pressure tower reflux device includes a negative-pressure tower reflux tank 39. The negative-pressure tower reflux tank 39 is connected to the top of the negative-pressure rectification tower 2 through a negative-pressure tower top product pipeline 40. A negative-pressure top first-stage condenser 41 is provided on the negative-pressure tower top product pipeline 40. The bottom of the negative-pressure tower reflux tank 39 is connected to the upper part of the negative-pressure rectification tower 2 through a negative-pressure tower reflux pipeline 42. A negative-pressure tower reflux extraction pump 43 is provided on the negative-pressure tower reflux pipeline 42. The negative-pressure tower reflux pipeline 42 is connected to a negative-pressure tower refined methanol product pipeline 44. A negative-pressure top cooler 45 is provided on the negative-pressure tower refined methanol product pipeline 44; the negative-pressure tower refined methanol product pipeline 44 is used to extract refined methanol, and the negative-pressure tower refined methanol product pipeline 44 can be connected to a refined methanol tank 46, and the refined methanol tank 46 is used to store the extracted refined methanol; the upper part of the negative-pressure tower reflux tank 39 is connected to a negative-pressure top second-stage condenser 48 through a top pipeline 47. The output ends of the negative-pressure top second-stage condenser 48 are respectively connected to a non-condensable gas extraction pipeline 49 and a condensate pipeline 50. The condensate pipeline 50 is connected to the negative-pressure tower reflux tank 39. A vacuum pump 51 is provided on the non-condensable gas extraction pipeline 49; the gas phase extracted from the top of the negative-pressure rectification tower 2 enters the negative-pressure tower reflux tank 39 after being condensed by the negative-pressure top first-stage condenser 41. A part of the liquid phase in the negative-pressure tower reflux tank 39 is refluxed to the negative-pressure rectification tower 2, and a part is extracted as refined methanol; the gas phase in the negative-pressure tower reflux tank 39 enters the negative-pressure top second-stage condenser 48 for condensation, the liquid phase returns to the negative-pressure tower reflux tank 39, and the gas phase is extracted through the non-condensable gas extraction pipeline 49. The extracted non-condensable gas enters the waste gas treatment system for treatment.

[0036] The output end of the secondary-pressure tower reboiler 21 is connected to the pressurized tower reflux tank 53 through a secondary-pressure tower reboiler output pipeline 52, and the output end of the atmospheric-pressure tower reboiler 22 is connected to the pressurized tower reflux tank 53 through an atmospheric-pressure tower reboiler output pipeline 54. The bottom of the pressurized tower reflux tank 53 is connected to the upper part of the pressurized rectification tower 3 through a pressurized tower reflux pipeline 55. A pressurized tower reflux extraction pump 56 is provided on the pressurized tower reflux pipeline 55. The pressurized tower reflux pipeline 55 is connected to a pressurized tower refined methanol product pipeline 57. A pressurized top cooler 58 is provided on the pressurized tower refined methanol product pipeline 57. The pressurized tower refined methanol product pipeline 57 can be connected to the refined methanol tank 46, and the refined methanol tank 46 is used to store the extracted refined methanol; the gas-phase refined methanol extracted from the top of the pressurized rectification tower 3 is used as a heat source to provide heat to the secondary-pressure tower reboiler 21 and the atmospheric-pressure tower reboiler 22 respectively. The liquid phase after heat exchange and temperature reduction with the secondary-pressure tower reboiler 21 and the atmospheric-pressure tower reboiler 22 enters the pressurized tower reflux tank 53. A part of the liquid phase in the pressurized tower reflux tank 53 is refluxed to the pressurized rectification tower 3, and a part is extracted as refined methanol.

[0037] The output end of the pre-column reboiler 19 is connected to the secondary-pressure column reflux device through the pre-column reboiler output pipeline 59; the secondary-pressure column reflux device includes a secondary-pressure column reflux tank 60, the secondary-pressure column reflux tank 60 is connected to the output end of the pre-column reboiler 19 through the pre-column reboiler output pipeline 59, the bottom of the secondary-pressure column reflux tank 60 is connected to the upper part of the secondary-pressure rectification column 4 through the secondary-pressure column reflux pipeline 61, a secondary-pressure column reflux extraction pump 62 is arranged on the secondary-pressure column reflux pipeline 61, and the secondary-pressure column reflux pipeline 61 is connected to the secondary-pressure column refined methanol extraction pipeline 63; the secondary-pressure column refined methanol extraction pipeline 63 can be connected to the refined methanol tank 46; the gaseous refined alcohol extracted from the top of the secondary-pressure rectification column 4 is used as a heat source to provide heat for the pre-column reboiler 19, the liquid phase after heat exchange and temperature reduction with the pre-column reboiler 19 enters the secondary-pressure column reflux tank 60, and a part of the liquid phase in the secondary-pressure column reflux tank 60 is refluxed to the secondary-pressure rectification column 4 and part is extracted as refined methanol.

[0038] The output end of the second vacuum column reboiler 24 is connected to the atmospheric column reflux device through the second vacuum column reboiler output pipeline 64; the atmospheric column reflux device includes an atmospheric column reflux tank 65, the atmospheric column reflux tank 65 is connected to the output end of the second vacuum column reboiler 24 through the second vacuum column reboiler output pipeline 64, the bottom of the atmospheric column reflux tank 65 is connected to the upper part of the atmospheric rectification column 5 through the atmospheric column reflux pipeline 66, an atmospheric column reflux extraction pump 67 is arranged on the atmospheric column reflux pipeline 66, the atmospheric column reflux pipeline 66 is connected to the atmospheric column refined methanol extraction pipeline 68, an atmospheric column top cooler 69 is arranged on the atmospheric column refined methanol extraction pipeline 68, and the atmospheric column refined methanol extraction pipeline 68 can be connected to the refined methanol tank 46; the above-mentioned secondary-pressure column refined methanol extraction pipeline 63 can be directly connected to the refined methanol tank 46, or the secondary-pressure column refined methanol extraction pipeline 63 can be connected to the atmospheric column refined methanol extraction pipeline 68, and the refined methanol extracted from the secondary-pressure rectification column 4 and the atmospheric rectification column 5 is mixed and then enters the refined methanol tank 46; the gaseous refined alcohol extracted from the top of the atmospheric rectification column 5 is used as a heat source to provide heat for the second vacuum column reboiler 24, the liquid phase after heat exchange and temperature reduction with the second vacuum column reboiler 24 enters the atmospheric column reflux tank 65, and a part of the liquid phase in the atmospheric column reflux tank 65 is refluxed to the atmospheric rectification column 5 and part is extracted as refined methanol.

[0039] In this embodiment, a refined methanol distillation device with a daily output of 2,350 tons is taken as an example. The ethanol content in the feed crude alcohol is calculated at 2,000 ppm (at the end of the catalyst), and the target value of refined alcohol is ≤10 ppm; the operating pressures, temperatures and refined alcohol extraction amounts of each column in this embodiment are as follows in the table:

[0040]

[0041] In this embodiment, the top heat of the pre-rectifying column 1, the pressurized rectifying column 3, the secondary-pressure rectifying column 4, and the atmospheric rectifying column 5 is fully utilized, and the steam unit consumption is significantly reduced, from the consumption of the traditional process to 0.5 - 0.55 tons of steam per ton of refined methanol, greatly reducing the energy consumption. Moreover, through the effective recovery and utilization of heat, the thermal efficiency of the entire rectifying system is improved, ensuring the reduction of the system operation cost, enhancing the economic benefits of the enterprise, and reducing the emissions of carbon dioxide and other pollutants, meeting the production concept of green environmental protection.

[0042] Embodiment Two:

[0043] The difference between this Embodiment One and Embodiment Two lies in that in this embodiment, the pre-rectifying column 1 is respectively connected to the vacuum rectifying column 2 and the second vacuum rectifying column 70, the vacuum rectifying column 2 and the second vacuum rectifying column 70 are respectively connected to the pressurized rectifying column 3, and the pre-rectifying column 1 is respectively connected to the vacuum rectifying column 2 and the second vacuum rectifying column 70 through the pre-column bottom product pipeline 8 and the first pre-column bottom product pipeline 71; the bottom of the second vacuum rectifying column 70 is connected to the vacuum column bottom product pipeline 10 through the second vacuum column bottom product pipeline 72, or directly connected to the pressurized rectifying column 3 through the second vacuum column bottom product pipeline 72, and the second vacuum column bottom product pipeline 72 passes through the first-stage feed pre-heater 12 and the second-stage feed pre-heater 13 of the pressurized column; a second vacuum column bottom pump 86 is provided on the second vacuum column bottom product pipeline 72; a second vacuum column reboiler 73 is provided on the second vacuum rectifying column 70, the top of the vacuum rectifying column 2 is connected to the input end of the second vacuum column reboiler 73 through the vacuum column top product pipeline 40, and the gas phase extracted from the top of the vacuum rectifying column 2 provides heat for the second vacuum column reboiler 73; the heat of the top of the vacuum rectifying column 2 is utilized to further reduce the steam unit consumption.

[0044] The output end of the second vacuum column reboiler 73 is connected to the vacuum column reflux device through the second vacuum column reboiler output pipeline 74; the vacuum column reflux device includes a vacuum column reflux tank 39, the vacuum column reflux tank 39 is connected to the output end of the second vacuum column reboiler 73 through the second vacuum column reboiler output pipeline 74, and the structure of the vacuum column reflux device is the same as that in Embodiment One and will not be specifically described here; the gas-phase refined methanol extracted from the top of the vacuum rectifying column 2 serves as a heat source to provide heat for the second vacuum column reboiler 73, and the liquid phase after heat exchange and temperature reduction with the second vacuum column reboiler 73 enters the vacuum column reflux tank 39. Part of the liquid phase in the vacuum column reflux tank 39 flows back to the vacuum rectifying column 2, and part is taken out as refined methanol; the gas phase in the vacuum column reflux tank 39 is condensed by the second-stage condenser 48 at the top of the vacuum column, the liquid phase returns to the vacuum column reflux tank 39, and the gas phase is taken out through the non-condensable gas extraction pipeline 49, and the extracted non-condensable gas enters the waste gas treatment system for treatment.

[0045] A negative-pressure tower two reflux device is provided at the top of the second negative-pressure rectification tower 70. The negative-pressure tower two reflux device includes a negative-pressure tower two reflux tank 75. The negative-pressure tower two reflux tank 75 is connected to the top of the second negative-pressure rectification tower 70 through a negative-pressure tower two top product extraction pipeline 76. A negative-pressure tower two primary condenser 77 is provided on the negative-pressure tower two top product extraction pipeline 76. The bottom of the negative-pressure tower two reflux tank 75 is connected to the upper part of the second negative-pressure rectification tower 70 through a negative-pressure tower two reflux pipeline 78. A negative-pressure tower two reflux extraction pump 79 is provided on the negative-pressure tower two reflux pipeline 78. The negative-pressure tower two reflux pipeline 78 is connected to a negative-pressure tower two refined methanol extraction pipeline 80. The negative-pressure tower two refined methanol extraction pipeline 80 can be directly connected to a refined methanol tank 46. In this case, a cooler needs to be provided on the negative-pressure tower two refined methanol extraction pipeline 80. In another form, the negative-pressure tower two refined methanol extraction pipeline 80 is connected to a negative-pressure tower refined methanol extraction pipeline 44. After the refined methanol extracted from the second negative-pressure rectification tower 70 and the refined methanol extracted from the second negative-pressure rectification tower 2 are mixed, they are jointly cooled by a negative-pressure tower top cooler 45 and then enter the refined methanol tank 46 for storage. The upper part of the negative-pressure tower two reflux tank 75 is connected to a negative-pressure tower two secondary condenser 82 through a top pipeline 81. The output ends of the negative-pressure tower two secondary condenser 82 are respectively connected to a non-condensable gas extraction pipeline 83 and a condensate pipeline 84. The condensate pipeline 84 is connected to the negative-pressure tower two reflux tank 75. A vacuum pump 87 is provided on the non-condensable gas extraction pipeline 83. The gas phase extracted from the top of the second negative-pressure rectification tower 70 enters the negative-pressure tower two reflux tank 75 after being condensed by the negative-pressure tower two primary condenser 77. The liquid phase in the negative-pressure tower two reflux tank 75 partially returns to the second negative-pressure rectification tower 70 and partially is extracted as refined methanol. The gas phase in the negative-pressure tower two reflux tank 75 enters the negative-pressure tower two secondary condenser 82 for condensation. The liquid phase returns to the negative-pressure tower two reflux tank 75, and the gas phase is extracted through the non-condensable gas extraction pipeline 83. The extracted non-condensable gas enters the waste gas treatment system for treatment.

[0046] In this embodiment, a waste water extraction pipeline 85 is connected to the lower part of the secondary pressure rectification tower 4 for discharging up-to-standard waste water.

[0047] Taking a refined methanol rectification device with a daily output of 2,350 tons as an example in this embodiment, the ethanol content in the feed crude alcohol is calculated at 2,000 ppm (at the end of the catalyst period), and the target value of refined alcohol is ≤ 10 ppm. The operating pressures, temperatures, and refined alcohol extraction amounts of each tower in this embodiment are as follows in the table:

[0048]

[0049] In this embodiment, a second vacuum distillation column 70 is provided, and the heat at the top of the vacuum distillation column 2 is also utilized to further reduce the steam specific consumption to 0.4 - 0.45 tons of steam per ton of refined methanol, and the energy-saving effect is more remarkable; by adding the second vacuum distillation column 70, deeper heat recovery is achieved, and the overall thermal efficiency of the system is improved; due to more efficient heat coupling, the operating cost of the system is further reduced, and the economic benefit is more obvious; the environmental impact is further reduced, which is conducive to realizing sustainable development and environmental protection.

[0050] In summary, due to the adoption of the above technical solutions, this application can significantly improve the energy utilization efficiency of the methanol distillation process, reduce production costs, and reduce environmental pollution, with remarkable economic and social benefits; the tower configuration and specific heat exchange network set in this application ensure the efficient utilization of heat and the reduction of energy consumption, realizing efficient heat energy utilization; and it can improve the distillation efficiency.

[0051] The devices, connection relationships, etc. not specifically described above all belong to the prior art, and the present utility model will not be specifically elaborated herein.

[0052] The preferred embodiments of this application have been described in detail above in conjunction with the accompanying drawings. However, this application is not limited to the specific details in the above embodiments. Within the scope of the technical concept of this application, various simple modifications can be made to the technical solutions of this application, and these simple modifications all fall within the protection scope of this application.

[0053] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any suitable manner without conflict. To avoid unnecessary repetition, various possible combination methods of this application will not be described separately.

[0054] In addition, any combination can be made between various different embodiments of this application, as long as it does not violate the idea of this application, it should also be regarded as the content disclosed in this application.

Claims

1. A methanol distillation device based on multi-effect thermal coupling, characterized in that, It includes a pre - rectifying column (1), a vacuum rectifying column (2), a pressurized rectifying column (3), a sub - pressurized rectifying column (4), and an atmospheric rectifying column (5) connected in sequence. A pre - column reboiler (19), a pressurized - column reboiler (20), a sub - pressurized - column reboiler (21), and an atmospheric - column reboiler (22) are respectively arranged on the pre - rectifying column (1), the pressurized rectifying column (3), the sub - pressurized rectifying column (4), and the atmospheric rectifying column (5). A first vacuum - column reboiler (23) and a second vacuum - column reboiler (24) are arranged at the lower part of the vacuum rectifying column (2). Among them, the gas phase extracted from the top of the sub - pressurized rectifying column (4) provides heat for the pre - column reboiler (19); the gas phase extracted from the top of the pressurized rectifying column (3) provides heat for the sub - pressurized - column reboiler (21) and the atmospheric - column reboiler (22) respectively; the gas phase extracted from the top of the pre - rectifying column (1) provides heat for the first vacuum - column reboiler (23); the gas phase extracted from the top of the atmospheric rectifying column (5) provides heat for the second vacuum - column reboiler (24).

2. The methanol rectification device based on multi-effect thermal coupling according to claim 1, characterized in that, The output end of the first vacuum - column reboiler (23) is connected to a pre - column reflux device. The pre - column reflux device includes an extraction reflux tank (32). An extraction water pipeline (35) is arranged on one side of the extraction reflux tank (32). A vent gas pipeline (36) is arranged at the top of the extraction reflux tank (32). The bottom of the extraction reflux tank (32) is connected to the upper part of the pre - rectifying column (1) through a pre - column reflux pipeline (37).

3. A methanol rectification device based on multi-effect thermal coupling according to claim 1, characterized in that, A vacuum - column reflux device is arranged at the top of the vacuum rectifying column (2).

4. A methanol rectification device based on multi-effect thermal coupling according to claim 1, characterized in that, The output ends of the sub - pressurized - column reboiler (21) and the atmospheric - column reboiler (22) are respectively connected to a pressurized - column reflux tank (53). The bottom of the pressurized - column reflux tank (53) is connected to the upper part of the pressurized rectifying column (3) through a pressurized - column reflux pipeline (55). The pressurized - column reflux pipeline (55) is connected to a pressurized - column refined methanol extraction pipeline (57).

5. A methanol rectification device based on multi-effect heat coupling according to claim 1, characterized in that, The output end of the pre - column reboiler (19) is connected to a sub - pressurized - column reflux device. The sub - pressurized - column reflux device includes a sub - pressurized - column reflux tank (60). The bottom of the sub - pressurized - column reflux tank (60) is connected to the upper part of the sub - pressurized rectifying column (4) through a sub - pressurized - column reflux pipeline (61). The sub - pressurized - column reflux pipeline (61) is connected to a sub - pressurized - column refined methanol extraction pipeline (63).

6. A methanol rectification device based on multi-effect heat coupling according to claim 1, characterized in that, The output end of the second vacuum - column reboiler (24) is connected to an atmospheric - column reflux device. The atmospheric - column reflux device includes an atmospheric - column reflux tank (65). The bottom of the atmospheric - column reflux tank (65) is connected to the upper part of the atmospheric rectifying column (5) through an atmospheric - column reflux pipeline (66). The atmospheric - column reflux pipeline (66) is connected to an atmospheric - column refined methanol extraction pipeline (68).

7. A methanol rectification device based on multi-effect heat coupling according to claim 1, characterized in that, The pre - rectifying column (1) is respectively connected to the vacuum rectifying column (2) and the second vacuum rectifying column (70). The vacuum rectifying column (2) and the second vacuum rectifying column (70) are respectively connected to the pressurized rectifying column (3). A second vacuum - column reboiler (73) is arranged on the second vacuum rectifying column (70). The gas phase extracted from the top of the vacuum rectifying column (2) provides heat for the second vacuum - column reboiler (73).

8. A methanol rectification device based on multi-effect heat coupling according to claim 1, characterized in that, The output end of the second vacuum - column reboiler (73) is connected to the vacuum - column reflux device.

9. A methanol rectification device based on multi-effect thermal coupling according to claim 4 or 8, characterized in that, The negative-pressure tower reflux device includes a negative-pressure tower reflux tank (39). The bottom of the negative-pressure tower reflux tank (39) is connected to the upper part of the negative-pressure distillation tower (2) through a negative-pressure tower reflux pipeline (42), and the negative-pressure tower reflux pipeline (42) is connected to the refined methanol extraction pipeline (44) of the negative-pressure tower. The upper part of the negative-pressure tower reflux tank (39) is connected to the secondary condenser (48) at the top of the negative-pressure tower through a top pipeline (47). The output ends of the secondary condenser (48) at the top of the negative-pressure tower are respectively connected with a non-condensable gas extraction pipeline (49) and a condensate pipeline (50). The condensate pipeline (50) is connected to the negative-pressure tower reflux tank (39), and a vacuum pump (51) is arranged on the non-condensable gas extraction pipeline (49).

10. A methanol rectification device based on multi-effect heat coupling according to claim 7, characterized in that, A negative-pressure tower two reflux device is arranged at the top of the negative-pressure distillation tower two (70). The negative-pressure tower two reflux device includes a negative-pressure tower two reflux tank (75). The bottom of the negative-pressure tower two reflux tank (75) is connected to the upper part of the negative-pressure distillation tower two (70) through a negative-pressure tower two reflux pipeline (78), and the negative-pressure tower two reflux pipeline (78) is connected to the refined methanol extraction pipeline (80) of the negative-pressure tower two. The upper part of the negative-pressure tower two reflux tank (75) is connected to the secondary condenser two (82) of the negative-pressure tower two through a top pipeline two (81). The output ends of the secondary condenser two (82) of the negative-pressure tower two are respectively connected with a non-condensable gas extraction pipeline two (83) and a condensate pipeline two (84). The condensate pipeline two (84) is connected to the negative-pressure tower two reflux tank (75), and a vacuum pump two (87) is arranged on the non-condensable gas extraction pipeline two (83).

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